A pendulum with the time period of $1 \mathrm{s}$ is losing energy due to damping. At a certain time, its energy is $45 \mathrm{J}$. If after completing $15$ oscillations its energy has become $15 \mathrm{J}$, then its damping constant (in ${\mathrm{s}}^{-1}$) will be

• A

  $\frac{1}{2}$
• B

  $\frac{1}{15}\ln 3$
• Correct answer
  C

  $\frac{1}{30}\ln 3$
• D

  $2$

Hence, the correct answer is option: 'C'.